&GAS: TABLE
The units to be used for the various quantities are:
----------------------------------------------------
Item Unit
----------------------------------------------------
Attachment coefficient 1/cm
Drift velocity cm/microsec
Ion mobility cm2/microsec.V
Longitudinal diffusion cm for 1 cm of drift
Lorentz angle degrees
Townsend coefficient 1/cm
Transverse diffusion cm for 1 cm of drift
----------------------------------------------------
The simple scaling laws used by Garfield to extrapolate to a
different pressure are listed in the table below. When using
Magboltz or MIX to compute the transport properties, you are
strongly advised to have the transport properties computed at
the relevant pressure and temperature, instead of relying on
the scaling laws.
------------------------------------------------------------
quantity scaling enter
------------------------------------------------------------
drift velocity v vs E/p v
ion mobility mu vs E/p mu
diffusion coefficients sigma.sqrt(p) vs E/p sigma.sqrt(p)
Townsend coefficient alpha/p vs E/p alpha/p
Attachment coefficient beta/p vs E/p beta/p
Lorentz angles - angle
------------------------------------------------------------
Example: the diffusion coefficient varies approximately with
pressure according to the formula:
sigma(p=p1)=sigma(p=p0)*sqrt(p0)/sqrt(p1)
hence sigma.sqrt(p) is approximately constant.
The dummy keyword can be used to comment out a column of the
gas tables. For instance, if you have prepared a table in which
both the transverse and longitudinal diffusion are present and
wish to assess the effect of transverse diffusion, then you
could do as in the example below.
------------------------------------------------------------
Original instruction New instruction
------------------------------------------------------------
table e/p trans-diff long-diff table e/p dummy long-diff
1 0.1 0.1 1 0.1 0.1
2 0.1 0.2 2 0.1 0.2
3 0.1 0.3 3 0.1 0.3
------------------------------------------------------------
Alternatively, you could have kept the original table followed
by a RESET TRANS-DIFF command.
Keyword index.
Formatted on 10/11/98.